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Special Report
New Faculty Members

 April 1999

 

 

 

The Power of Electronics

Work done through a Ford-sponsored CPES Fellowship shows an advanced soft-switching inverter developed to reduce electromagnetic interference. "Traction motor drives today can interfere with car radios, mobile phones, and even the computerized controller," said Jason Lai. "With this inverter we were able to reduce the interference in a wide frequency range." Below: Through a project of the Partnership for the Next Generation Vehicle, faculty and students in the Center for Power Electronics Systems' laboratories are developing a soft-switching inverter (pictured on the left), to replace the traditional band-switching inverter (pictured on the right).

 

I like to build real things with my own hands - especially if it involves electricity and machines."

As a power electronics expert, Jason Lai has had many opportunities to enjoy systems built by his own hands - from electric utility products for power quality to soft switch choppers for magnetic levitation.

Lai joined the Virginia Tech faculty in 1996 as an associate professor after serving as the power electronics lead scientist at Oak Ridge National Laboratory and as an adjunct associate professor at Georgia Tech. Prior to that, he worked with the Electric Power Research Institute (EPRI) in the Power Electronics Applications Center (PEAC).

Lai joined PEAC immediately after earning his Ph.D. from the University of Tennessee in 1989. While there, he served as manager of the power electronics section that developed products to solve power quality problems for electric utilities. He has continued working on PEAC projects since coming to Tech, developing high-power converters for utility applications.

When he moved to Oak Ridge, he worked on power inverter drives for nuclear applications. "The chief application there was very interesting," he said. "We were working on the high-speed machine drive for nuclear fuel separation."

His team also worked for the Department of Energy on the Partnership for the Next Generation Vehicle project. "We were developing motor drives for electric cars."

Power electronics is an enabling technology for many applications, he explained. "You don't see a lot of power electronics products in themselves, but many products require power electronics. For example, people buying electric vehicles are buying the car; they do not consider the inverter. However, if you do not have an inverter, you cannot drive the car."
Lai is a faculty member of the NSF Center for Power Electronics Systems that is headquartered at Virginia Tech, and he has continued his work on electric vehicles in the university laboratories. With Fred C. Lee, he has developed a bi-directional charger for a traditional battery-and-fuel-cell vehicle. "One side can take the energy from a normal low-voltage battery to obtain the high voltage and to start up the fuel cell compressor, and after establishing the voltage from the fuel cell, the high voltage can charge back to the low-voltage battery," he explained. "For a pure battery-powered electric vehicle, you don't need our bi-directional charger, but for fuel cell-powered electric vehicle, you can't run the car without this bi-directional charger," he said. The project was originally sponsored by Oak Ridge National Lab and is now transferred to the automotive industry.

He has also been developing soft switching inverters for traction motor drives to replace the car's engine. "The bi-directional charger has not been developed in industry and is unique and crucial today, but the technology involved in the traction drive is most difficult," he explained. "We are trying to improve today's drives by improving efficiency and performance and reducing the noise."

Another major project in which he is involved concerns the development of power electronics building blocks. "These are different power modules that can directly connect to a common dc bus," he said. "They are different from today's ac power systems, in that they distribute power through a common dc bus to different loads through power conversion equipment."

Other efforts include improving a chopper for magnetic levitation with soft-switching, working to reduce electromagnetic interference for inverter drives, and developing measurement techniques for power electronics parasitic components.

Lai believes his experience is very helpful in teaching electronics at the undergraduate level and power electronics at both under- and graduate levels. "I probably teach a more practical course than others," he said. "I use a lot of practical concepts and design- and application-oriented examples."

Ideally, he would like all students to be required to develop a working system from concept through testing. "Using power electronics as an example, I would like to see students design and build a power converter for certain applications, such as power supplies, ballasts, or motor drives. I would like them to start from concept, give the specifications, go to the tables for design, use the computer simulation tools, build the converters in the lab, and make it work."

"Students learn much through this comprehensive implementation - not just the mathematical equations. When they have one experience, they can translate it to others," he said.

Lai believes that Virginia Tech provides this type of opportunity to electrical and computer engineering students. "We provide the environment, facilities, and courses. My only question is: do the students take advantage of it?"

He also believes that more students should take advantage of power electronics education. "I think this country needs more power electronics engineers. Engineers today learn power electronics on the job. Most of them do not have the formal training they need to develop the best systems and advance the field. That's a handicap."

 

The Bradley Department
of Electrical and Computer Engineering
Virginia Tech


Last Updated, July 10, 1999
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